Weight back

my son is working with a pitching coach and his problem is,he has a hard time keeping his weight back,when his front leg comes up he is fine,but when his front leg starts to come down his upper body comes with it,his coach says his upper body should stay back intill his foot almost touch the ground,anyone have any thoughts?is there any drills that might help?

This site has some good drills for young pitchers. http://www.thecompletepitcher.com/pitching_drills.htm
The one drill I think might help best with your son is the “Quick Hands Drill” since this drill has him starting with his lead foot already planted out front.
This video basically shows the “quick hand drill”. - YouTube

I use an NPA drill called the Hershiser Drill. You stand sideways to a padded wall or chain link fence with your glove side shoulder facing the wall/fence. Then you lift your knee and push your hip or back pocket into the wall. The hip or back pocket should be the first and only part of your body to touch the wall/fence. You can reverse rotate the shoulders as if you’re “showing your number” to help.

Start with your pivot foot about one shoe length from the wall/fence. Then progress to the pivot foot being two shoe lengths from the wall/fence. Wear a glove. And practice pushing the hip early - before peak of knee lift or even right after the stride foot lifts off the ground.

This drill helps teach leading with the front hip and keep head and shoulders slightly behind the front hip.

As a drill only, you could have him keep his knee up longer as he starts to push off with his pivot foot. When he begins to push off with the pivot foot (his knee will be waist high) have him point his knee towards the catcher as usual, but have him keep his knee up longer, for as long as possible until he has to lower it for landing. Remember, this is not mechanics but simply a drill to help keep the weight back. Hope it helps!